Etymological weirdness:

First, “grocer” was “one who sold things by the gross (in large quantities)”—basically a wholesaler. Then the things they sold became known as “grocery”

Since much of what was sold was foods and spices, “grocery” drifted to mainly mean “foods”. And the people who sold foods, even though it was mostly in quantities for personal use, were the purveyors of grocery, so… “grocers”

This reinforced itself in US English, so that the stuff you buy at a grocer was called “groceries”. And then the place you buy them—a store of groceries—becomes a “grocery store” (regional; some places use “market”)

What a lovely little tornado!